This invention is for a process for recovery of fluid hydrocarbons from solid carbonaceous materials by the pyrolysis of the carbonaceous material.
Hydrocarbons resulting from pyrolysis of solid carbonaceous materials, such as coal and oil shale, usually are of relatively low economic value due to their high carbon to hydrogen ratio and tendency to self-polymerize due to the presence of many unsaturated alkene and alkyne bonds. Therefore, to improve the economics of the pyrolysis processes, the low value hydrocarbons typically are hydrogenated in a hydrogenation reactor with hydrogen gas produced in a hydrogen generating plant after they are recovered from the effluent stream from the pyrolysis reaction zone. This is an expensive process due to the operating and capital costs associated with the hydrogen gas generating plant and the hydrogenation reactor. Sometimes the low value hydrocarbons are not hydrogenated until after they are cooled and condensed in a product recovery operation. This is thermally inefficient unless the hydrocarbons are reheated, and reheating is both expensive and wasteful of thermal energy.
When catalytic hydrogenation is used, the liquid products generally are subjected to a solids removal step wherein carbon containing residue of pyrolysis and ash contaminants of very small particle sizes are removed from the liquids. The cost and efficiency of this step is strongly dependent on the quality of the liquids. Solids contaminant removal improves in terms of efficiency and costs as the quality of the liquids improves. Therefore, it would be beneficial to hydrogenate the hydrocarbon product before solids removal.
Squires in U.S. Pat. No. 3,855,070 discloses a process in which coal is pyrolyzed to yield char and hydrocarbons while the hydrocarbons are simultaneously hydrogenated. In Squires' process, the heat for pyrolysis is obtained from hot particulate char, and the hydrogen for the hydrogenation reaction is obtained by presumably reacting a portion of the product char with steam in a fast fluidized bed. This process has high capital and operating costs because of the need for two char loops, one for heating char used as the hot particulate source of heat and a second loop for producing hydrogen gas by reacting steam with char.
Therefore, there is a need for an efficient low cost process for the recovery of fluid hydrocarbons from coal where the fluid hydrocarbons have been upgraded by hydrogenation.